Search results for " Interferometry"
showing 10 items of 170 documents
A simple technique for measurement of corneal thickness.
1998
Measurement of corneal thickness has potential benefit both in the fitting of contact lenses and in monitoring any pathology that could affect corneal thickness. Corneal thickness measurement is undertaken using an accessory to the biomicroscope, the optical pachometer, or by means of expensive apparatus such as the ultrasonic pachometer. There are other complex methods, such as laser Doppler interferometry, or ultrasonic rasters of the cornea. In this study, an easier and low cost method, based on the measurement of the optical section formed of the cornea by the biomicroscope illumination system, is proposed. The advantages of this new method are the simplicity of its experimental set-up …
Agreement of predicted intraocular lens power using swept-source optical coherence tomography and partial coherence interferometry
2021
PURPOSE To analyze the agreement of the predicted intraocular lens (IOL) power obtained with ANTERION, IOLMaster 700 and Pentacam AXL biometers. METHODS We calculated the monofocal and trifocal IOL power using the SRK/T, Haigis, Barrett Universal II and Hoffer Q formulas for 106 eyes. IOL power agreement between devices was evaluated using the Bland-Altman method. RESULTS We found significant differences between biometers comparisons (p 0.05), with the same outcomes for medium- and long-eyes. No significant differences were found using the SRK/T, Haigis, or Hoffer Q formulas for short-eyes (p > 0.1). However, Barrett Universal II formula produced significant differences (p < 0.05) and thes…
Graphic representation of data resulting from measurement comparison trials in cataract and refractive surgery.
2003
* BACKGROUND AND OBJECTIVES: The evaluation of new diagnostic measurement devices allows intraindividual comparison with an established standard method. However, reports in journal articles often omit the adequate incorporation of the intraindividual design into the graphic representation. * PATIENTS AND METHODS: This article illustrates the drawbacks and the possible erroneous conclusions caused by this misleading practice in terms of recent method comparison data resulting from axial length measurement in 220 consecutive patients by both applanation ultrasound and partial coherence interferometry. * RESULTS: Graphic representation of such method comparison data should be based on boxplots…
Dynamic laser speckle analyzed considering inhomogeneities in the biological sample
2017
Dynamic laser speckle phenomenon allows a contactless and nondestructive way to monitor biological changes that are quantified by second-order statistics applied in the images in time using a secondary matrix known as time history of the speckle pattern (THSP). To avoid being time consuming, the traditional way to build the THSP restricts the data to a line or column. Our hypothesis is that the spatial restriction of the information could compromise the results, particularly when undesirable and unexpected optical inhomogeneities occur, such as in cell culture media. It tested a spatial random approach to collect the points to form a THSP. Cells in a culture medium and in drying paint, repr…
Spatially multiplexed interferometric microscopy with partially coherent illumination
2016
We have recently reported on a simple, low cost, and highly stable way to convert a standard microscope into a holographic one [Opt. Express 22, 14929 (2014)]. The method, named spatially multiplexed interferometric microscopy (SMIM), proposes an off-axis holographic architecture implemented onto a regular (nonholographic) microscope with minimum modifications: the use of coherent illumination and a properly placed and selected one-dimensional diffraction grating. In this contribution, we report on the implementation of partially (temporally reduced) coherent illumination in SMIM as a way to improve quantitative phase imaging. The use of low coherence sources forces the application of phase…
Evaluation of continuous filament mat influence on the bending behaviour of GFRP pultruded material via Electronic Speckle Pattern Interferometry
2017
Abstract Pultrusion is a process allowing the production of unidirectional (roving) fibre-reinforced polymer (FRP) structural elements with constant cross section. Recently, also civil engineers focused their attention on pultruded composite materials as alternative to traditional ones (e.g., concrete, steel). Furthermore, to improve the transverse strength and stiffness with respect to the fibres direction, continuous filament mat (CFM) is often placed within the stacking sequence. The CFM influence on the global mechanical behaviour is not considered by appropriate actual international standards. In this paper, the influence of the CFM layers on the mechanical behaviour of glass fibres pu…
Laser Vibrometer Interferometry for Speckle Patterns Tracking Systems
2017
In this paper we propose a modulated laser system combining a speckle pattern tracking method for surface tilting changes sensing with an interferometer for surface z-axis changes sensing at the same scan time.
Young's modulus measurement of the radius bone using a shearing interferometer with carrier fringes
2010
Abstract A technique for measuring Young's modulus of the radius bone by using electronic speckle-shearing pattern interferometry is proposed. The technique is based on the introduction of carrier fringes and the use of a phase unwrapping algorithm to obtain a phase map corresponding to the out-of-plane displacements of a radius bone without sign ambiguities. The carrier fringes are obtained by the correlation algorithm of two consecutive speckle fields with a translation of the illuminating beam between each recording, then the spatial synchronous detection (SSD), an unwrapping phase algorithm and integration process along shear direction are successfully applied for obtaining a displaceme…
Residual strain and stress analysis by speckle interferometry combined with the drill of a groove
2007
A new method for residual stresses determination combining Electronic Speckle Pattern Interferometry (ESPI) with the machining of a groove. The internal stress field is perturbed as the depth of the groove is increased incrementally [1]. The structure finds a new equilibrium state generating displacements which are measured using ESPI. This method was tested on an aluminium alloy plate treated locally by ultrasonic shot-peening. The investigation of the images obtained with the phase shifting technique and fringe patterns makes it possible to analyze, simultaneously, the stress profile along two directions: along the depth of the structure, and along the groove direction.
Toward fast malaria detection by secondary speckle sensing microscopy
2012
Diagnosis of malaria must be rapid, accurate, simple to use, portable and low cost, as suggested by the World Health Organization (WHO). Despite recent efforts, the gold standard remains the light microscopy of a stained blood film. This method can detect low parasitemia and identify different species of Plasmodium. However, it is time consuming, it requires well trained microscopist and good instrumentation to minimize misinterpretation, thus the costs are considerable. Moreover, the equipment cannot be easily transported and installed. In this paper we propose a new technique named "secondary speckle sensing microscopy" ((SM)-M-3) based upon extraction of correlation based statistics of s…